• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.3
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• pp.265-274
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• 2022

This paper proposes a machine learning-based screening algorithm to build the retired battery pack of the energy storage system. The proposed algorithm creates the dataset of various performance parameters of the retired battery, and this dataset is preprocessed through a principal component analysis to reduce the overfitting problem. The retried batteries with a large deviation are excluded in the dataset through a density-based spatial clustering of applications with noise, and the K-means clustering method is formulated to select the group of the retired batteries to satisfy the deviation requirement conditions. The performance of the proposed algorithm is verified based on NASA and Oxford datasets.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.3
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• pp.139-146
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• 2019

As the number of electric vehicles (EVs) in Jejudo Island increases, the secondary use of EV batteries is becoming increasingly mandatory not only in reducing greenhouse gas emissions but also in promoting resource conservation. For the secondary use of EV batteries, their capacity and performance at the end of automotive service should be evaluated properly. In this study, the battery state information from the on-board diagnostics or OBD2 port was acquired in real time while driving three distinct routes in Jejudo Island, and then the battery operating characteristics were assessed with the driving routes. The route with higher altitude led to higher current output, i.e., higher C-rate, which would reportedly deteriorate state of health (SOH) faster. In addition, the SOH obtained from the battery management system (BMS) of a 2017 Kia Soul EV with a mileage of 55,000 km was 100.2%, which was unexpectedly high. This finding was confirmed by the SOH estimation based on the ratio of the current integral to the change in state of charge. The SOH larger than 100% can be attributed to the rated capacity that was lower than the nominal capacity in EV application. Therefore, considering the driving environment and understanding the SOH estimation process will be beneficial and necessary in evaluating the capacity and performance of retired batteries for post-vehicle applications.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.357-363
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• 2021

Eco-friendly hybrid railroad propulsion system with fuel-cell and battery was suggested to reduce carbon dioxide gas and replace retired diesel railroads. Lithium-ion battery with high energy/power density and long lifetime is selected as the energy source at the battery side due to its excellent performance. However, the performance of lithium-ion batteries was affected by temperature, current rate, and operating condition. Temperature is known to be the most influential factor in changing battery parameters. In addition, appropriate thermal management is required to ensure the safe and effective operation of lithium-ion battery. Electro-thermal coupled model with varying parameter depends on temperature, and state-of-charge (SOC) is suggested to estimate battery temperature. The electric-thermal coupled model contains diffusion current using parameter identification by adaptive control algorithm when considering thermal diffusion effect. An experiment under forced convection was conducted using cylindrical cell and 18 parallel-connected battery module to demonstrate the method.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.345-346
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• 2016

The grid-connected energy storage systems, which could increase the reliability, efficiency, and cleanliness of the grid is presently restricted by the high cost of batteries. This problems could be solved by batteries retired from automotive services. These batteries can provide a low-cost system for energy storage and other applications such as residential applications and renewable energy integration. This paper gives an overview of technical requirements for the re-use of the electric vehicle batteries in energy storage systems.Firstly, the motivation of research is introduced. Secondly, the technologies needed for the re-use of the battery are introduced such asidentification of the battery characteristics, grading of the aged batteries, identification of the state-of-charge and state-of-health of the battery and suitable power electronic converter topologies. In addition the control strategy to maximize the battery lifespan and bypass the faulty batteries is presented and one-stop solution to implement the above mentioned technologies are also given.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.3
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• pp.167-175
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• 2021

Reusing electric vehicle batteries after they have been retired from mobile applications is considered a feasible solution to reduce the demand for new material and electric vehicle costs. However, the evaluation of the value and the performance of second-life batteries remain a problem that should be solved for the successful application of such batteries. The present work aims to estimate the remaining useful life of Li-ion batteries through the neuro-fuzzy system with the equivalent circuit parameters obtained by Electrochemical Impedance Spectroscopy (EIS). To obtain the impedance spectra of the Li-ion battery over the life, a 18650 cylindrical cell has been aged by 1035 charge/discharge cycles. Moreover, the capacity and the parameters of the equivalent circuit of a Li-ion battery have been recorded. Then, the data are used to establish a neuro-fuzzy system to estimate the remaining useful life of the battery. The experimental results show that the developed algorithm can estimate the remaining capacity of the battery with an RMSE error of 0.841%.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.159-161
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• 2018

지난 수년 간 다량으로 배출되고 있는 폐 배터리를 에너지 저장장치(ESS)로서 재활용하고자 하는 연구가 활발히 진행되고 있다. 이러한 ESS 시스템에는 사용하는 배터리마다의 규격이나 이전 사용 시 수명, 배출 시 상태의 차이가 존재하기 때문에 각 배터리 간 셀밸런싱 시스템이 필수로 요구된다. 현재까지 직렬형, 병렬형 등이 연구되고 있지만 모듈화나 신뢰성 등을 만족 시키기 위해서는 병렬형이 유리하다. 본 논문에서는 양방향 리니어 레귤레이터를 사용하며 셀 벨런싱 회로가 없는 병렬형 충방전 시스템을 제안하고자 한다.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.108-109
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• 2017

전기자동차 보급 확대로 인해 2018년부터 전 세계적으로 폐배터리가 다량으로 배출될 것으로 예상되어 폐 배터리를 에너지저장장치(ESS)로 재활용하는 방안이 연구되고 있다. 하지만 배터리간 규격이나 수명, 상태의 차이가 존재하기 때문에 셀밸런싱 시스템이 필수로 요구된다. 기존에는 이러한 시스템으로 직렬형 시스템을 채용하고 있지만 모듈화나 신뢰성 등 시스템이 요구하는 조건을 만족시키기 어렵다. 이에 따라 본 논문에서는 기존 시스템과 차별화 된 분산 충 방전 병렬 시스템을 제안하고 그에 사용되는 전력조절기를 소개하고자 한다.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.73-75
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• 2019

폐배터리를 조합하여 배터리 팩을 구성 시, 사용환경이 상이한 폐배터리 간의 전압/SOC의 편차가 존재하여 장기간 사용시 과충전/과방전과 같은 안전상을 문제가 발생할 가능성이 크다. 따라서 본 논문에서는 확장 칼만 필터를 기반 센서 융합 방법을 사용하여 폐배터리 팩의 셀 간 SOC 불균형을 추정하는 알고리즘을 제안한다. 검증은 셀간 전압 불균형이 있는 노화된 배터리 팩에 임의의 전류 프로파일을 인가하여 제안된 알고리즘을 검증한다.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.54-55
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• 2015

본 논문에서는 리튬-이온(Lithium-ion) 폐배터리 효율적인 재활용을 위한 발전된 SOC 추정방법의 필요성과 간단한 개념을 언급하고자 한다. 배터리는 노화되면 용량이 줄어들고 임피던스의 크기가 증가해 기존의 새 배터리의 SOC 추정방법으로는 정확한 추정이 어렵다. 따라서, 폐배터리를 안전하고 효율적으로 사용하기 위해서는 그에 맞는 SOC 추정방법이 필요하다. 따라서, 폐배터리의 간단한 개념을 설명하고, 동일한 배터리 등 가회로모델과 EKF 알고리즘을 적용한 새 리튬-이온 셀과 노화된 리튬-이온셀의 SOC 추정결과를 비교하고 노화에 따른 배터리 파라미터값의 변화를 분석해봄으로서 발전된 SOC 추정방법의 필요성에 대해 논의해보고자 한다.

• Journal of the Korean Society of Safety
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• v.39 no.2
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• pp.38-43
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• 2024

Recently, with the expanding market for electronic devices and electric vehicles, secondary battery usage has been on the rise. Lithium-ion batteries are particularly popular due to their fast charging times and lightweight nature compared to other types of batteries. A secondary battery consists of four components: anode, cathode, electrolyte, and separator. Generally, the positive and negative electrode materials of secondary batteries are composed of an active material, a binder, and a conductive material. Acetylene Black (AB) is utilized to enhance conductivity between active material particles or metal dust collectors, preventing the binder from acting as an insulator. However, when recycling waste batteries that have been subject to high usage, there is a risk of fire and explosion accidents, as accurately identifying the characteristics of Acetylene Black dust proves to be challenging. In this study, the lower explosion limit for Acetylene Black dust with an average particle size of 0.042 ㎛ was determined to be 153.64 mg/L using a Hartmann-type dust explosion device. Notably, the dust did not explode at values below 168 mg, rendering the lower explosion limit calculation unfeasible. Analysis of explosion delay times with varying electrode gaps revealed the shortest delay time at 3 mm, with a noticeable increase in delay times for gaps of 4 mm or greater. The findings offer fundamental data for fire and explosion prevention measures in Acetylene Black waste recycling processes via a predictive model for lower explosion limits and ignition delay time.